There is nothing wrong with an 18 month old only having 2 teeth. Some babies teeth just come in later. That can mean they will have better and stronger teeth as an adult.
Putting pasta and potatoes together are not the best idea. It is a double starch and you want to feed and 18 month old something that is at least kind of healthy.
Does the vegtarian eat eggs?
Spaghetti sauce with zuchini, and yellow crooked neck squash. Served on top of a mashed baked potato.
Or steam some potatoes, then toss with a little olive oil, peas, carrots, and maybe even some green beans. Use the no salt added canned ones as they are much sodter. Mash just a tad. Then add a little bit of sour cream if you wish.
Make an egg scramble with is like a baby omlet.
Saute up some mushrooms, bell peppers, and potatoes (micorwave the first of steam them so they cook easier). Pour some lightly whisked egg sover the top and keep moving the eggs and veggies around, When the egg is cooked sprinkle with shredded cheese.
Make mashed potatoe pancakes and add any soft veggie tothis recipes. Just as very soft carrots, corn, peas, green beans etc... and maybe even a bit of chicken chopped very very small.
A good recipe for left over mashed taters.
1/2 cup flour
1/4 tsp salt
1 egg lightly beaten
1 tsp baking powder
1 cup mashed potatoes-warmed just a bit
1 tsp dried parsely
Or you can make these into potato pancakes and just mash the balls flat.
Good luck and enjoy.